Ignition timing control system for internal combustion engine

Abstract

An ignition timing control system for an internal combustion engine, for controlling an ignition timing of the engine, is provided. A charging efficiency of the engine is calculated according to the intake air flow rate and the engine rotational speed which are detected, and a knock limit ignition timing is calculated according to the engine rotational speed and the charging efficiency. A knock correction value is calculated according to the knocking detection result by a knock sensor, and a learning parameter table, in which first and second learning parameters are set, is updated based on the engine rotational speed and the knock correction value when the knocking is detected. The learning parameter table is retrieved according to the engine rotational speed, to calculate the first and second learning parameters. Each-cylinder correction values are calculated corresponding respectively to a plurality of cylinders of the engine using the charging efficiency, the first learning parameter, and the second learning parameter and the ignition timing of the engine is controlled using the knock limit ignition timing and the each-cylinder correction value.

The invention claimed is: 
     
       1. An ignition timing control system for an internal combustion engine, for controlling an ignition timing of said engine, said ignition timing control system being characterized by comprising:
 intake air flow rate detecting means for detecting an intake air flow rate of said engine; 
 rotational speed detecting means for detecting a rotational speed of said engine; 
 charging efficiency calculating means for calculating a charging efficiency of said engine according to the intake air flow rate and the engine rotational speed which are detected; 
 knock limit ignition timing calculating means for calculating a knock limit ignition timing according to the engine rotational speed and the charging efficiency; 
 knocking detecting means for detecting a knocking of said engine; 
 knock correction value calculating means for calculating a knock correction value according to the detected result by said knocking detecting means; 
 learning means for updating a learning parameter table based on the engine rotational speed and the knock correction value when the knocking is detected, wherein first and second learning parameters are set in the learning parameter table; 
 learning parameter calculating means for retrieving the learning parameter table according to the engine rotational speed, to calculate the first and second learning parameters; 
 each-cylinder correction value calculating means for calculating each-cylinder correction values corresponding respectively to a plurality of cylinders of said engine using the charging efficiency, the first learning parameter, and the second learning parameter; and 
 ignition timing calculating means for calculating an ignition timing of said engine using the knock limit ignition timing and the each-cylinder correction value, 
 wherein first and second learning parameters indicate a relationship between the charging efficiency and the each-cylinder correction value. 
 
     
     
       2. An ignition timing control system according to  claim 1 , wherein said each-cylinder correction value calculating means calculates the each-cylinder correction value by applying a difference between the charging efficiency and a reference value of the charging efficiency, to a linear expression containing the first and second learning parameters. 
     
     
       3. An ignition timing control system according to  claim 2 , wherein the reference value is set to a value greater than 100%. 
     
     
       4. An ignition timing control system according to  claim 1 , wherein said knock limit ignition timing calculating means includes:
 basic knock limit ignition timing calculating means for calculating a basic knock limit ignition timing according to the charging efficiency; and 
 rotational speed correction value calculating means for calculating a rotational speed correction value according to the engine rotational speed, 
 wherein said knock limit ignition timing calculating means calculates the knock limit ignition timing by correcting the basic knock limit ignition timing with the rotational speed correction value. 
 
     
     
       5. An ignition timing control system according to  claim 1 , wherein said engine has a valve operating characteristic varying mechanism for continuously varying an operating phase of at least one intake valve of said engine, and
 said knock limit ignition timing calculating means includes: 
 basic knock limit ignition timing calculating means for calculating a basic knock limit ignition timing according to the charging efficiency; 
 rotational speed correction value calculating means for calculating a rotational speed correction value according to the engine rotational speed; 
 inclination coefficient calculating means for calculating an inclination coefficient according to the charging efficiency and the engine rotational speed; and 
 operating phase correction value calculating means for calculating an operating phase correction value by multiplying an operating phase of the at least one intake valve by the inclination coefficient, 
 wherein said knock limit ignition timing calculating means calculates the knock limit ignition timing by correcting the basic knock limit ignition timing with the rotational speed correction value and the operating phase correction value. 
 
     
     
       6. An ignition timing control method for an internal combustion engine, for controlling an ignition timing of said engine, said ignition timing control method being characterized by comprising the steps of:
 a) detecting an intake air flow rate of said engine; 
 b) detecting a rotational speed of said engine; 
 c) calculating a charging efficiency of said engine according to the intake air flow rate and the engine rotational speed which are detected; 
 d) calculating a knock limit ignition timing according to the engine rotational speed and the charging efficiency; 
 e) detecting a knocking of said engine; 
 f) calculating a knock correction value according to the detected result by said step e); 
 g) updating a learning parameter table based on the engine rotational speed and the knock correction value when the knocking is detected, wherein first and second learning parameters are set in the learning parameter table; 
 h) retrieving the learning parameter table according to the engine rotational speed, to calculate the first and second learning parameters; 
 i) calculating each-cylinder correction values corresponding respectively to a plurality of cylinders of said engine using the charging efficiency, the first learning parameter, and the second learning parameter; and 
 j) calculating an ignition timing of said engine using the knock limit ignition timing and the each-cylinder correction value, 
 wherein the first and second learning parameters indicate a relationship between the charging efficiency and the each-cylinder correction value. 
 
     
     
       7. An ignition timing control method according to  claim 6 , wherein the each-cylinder correction value is calculated by applying a difference between the charging efficiency and a reference value of the charging efficiency, to a linear expression containing the first and second learning parameters. 
     
     
       8. An ignition timing control method according to  claim 7 , wherein the reference value is set to a value greater than 100% in said step i). 
     
     
       9. An ignition timing control method according to  claim 6 , wherein said step d) includes:
 k) calculating a basic knock limit ignition timing according to the charging efficiency; and 
 l) calculating a rotational speed correction value according to the engine rotational speed, 
 wherein the knock limit ignition timing is calculated in said step d) by correcting the basic knock limit ignition timing with the rotational speed correction value. 
 
     
     
       10. An ignition timing control method according to  claim 6 , wherein said engine has a valve operating characteristic varying mechanism for continuously varying an operating phase of at least one intake valve of said engine, and
 said step d) includes: 
 m) calculating a basic knock limit ignition timing according to the charging efficiency; 
 n) calculating a rotational speed correction value according to the engine rotational speed; 
 o) calculating an inclination coefficient according to the charging efficiency and the engine rotational speed; and 
 p) calculating an operating phase correction value by multiplying an operating phase of the at least one intake valve by the inclination coefficient, 
 wherein the knock limit ignition timing is calculated in said step d) by correcting the basic knock limit ignition timing with the rotational speed correction value and the operating phase correction value. 
 
     
     
       11. A computer program embodied on a computer-readable storage medium for causing a computer to implement an ignition timing control method for an internal combustion engine, for controlling an ignition timing of said engine, said ignition timing control method being characterized by comprising the steps of:
 a) detecting an intake air flow rate of said engine; 
 b) detecting a rotational speed of said engine; 
 c) calculating a charging efficiency of said engine according to the intake air flow rate and the engine rotational speed which are detected; 
 d) calculating a knock limit ignition timing according to the engine rotational speed and the charging efficiency; 
 e) detecting a knocking of said engine; 
 f) calculating a knock correction value according to the detected result by said step e); 
 g) updating a learning parameter table based on the engine rotational speed and the knock correction value when the knocking is detected, wherein first and second learning parameters are set in the learning parameter table; 
 h) retrieving the learning parameter table according to the engine rotational speed, to calculate the first and second learning parameters; 
 i) calculating each-cylinder correction values corresponding respectively to a plurality of cylinders of said engine using the charging efficiency, the first learning parameter, and the second learning parameter; and 
 j) calculating an ignition timing of said engine using the knock limit ignition timing and the each-cylinder correction value, 
 wherein the first and second learning parameters indicate a relationship between the charging efficiency and the each-cylinder correction value. 
 
     
     
       12. A computer program according to  claim 11 , wherein the each-cylinder correction value is calculated by applying a difference between the charging efficiency and a reference value of the charging efficiency, to a linear expression containing the first and second learning parameters. 
     
     
       13. A computer program according to  claim 12 , wherein the reference value is set to a value greater than 100% in said step i). 
     
     
       14. A computer program according to  claim 11 , wherein said step d) includes:
 k) calculating a basic knock limit ignition timing according to the charging efficiency; and 
 l) calculating a rotational speed correction value according to the engine rotational speed, 
 wherein the knock limit ignition timing is calculated in said step d) by correcting the basic knock limit ignition timing with the rotational speed correction value. 
 
     
     
       15. A computer program according to  claim 11 , wherein said engine has a valve operating characteristic varying mechanism for continuously varying an operating phase of at least one intake valve of said engine, and
 said step d) includes: 
 m) calculating a basic knock limit ignition timing according to the charging efficiency; 
 n) calculating a rotational speed correction value according to the engine rotational speed; 
 o) calculating an inclination coefficient according to the charging efficiency and the engine rotational speed; and 
 p) calculating an operating phase correction value by multiplying an operating phase of the at least one intake valve by the inclination coefficient, 
 wherein the knock limit ignition timing is calculated in said step d) by correcting the basic knock limit ignition timing with the rotational speed correction value and the operating phase correction value.